Ofloxacin (I), ((.+-.)-9-fluoro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-2,3-dihydro-7H -pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid) is known and employed as an excellent synthetic antibacterial agent.
Ofloxacin has an asymmetric carbon atom at the 3-position and is obtained as a racemic mixture. Of the two isomers, the 3S-methyl compound (IS) which is represented by the following formula was confirmed to have higher activity and reduced toxicity in comparison with the racemic compound or 3R-methyl compound (IR). ##STR1##
The synthesis of compound represented by the formula (IS) was achieved by converting the optically active benzoxazine intermediates which were obtained by the optical resolution of appropriate racemic benzoxazine derivatives, as described in EP-A No. 206,283.